"The perfect soul rejoices more in the differences among people . . ."
The quotation is actually a conflation by Vida Scudder in her Disciple of a Saint.
The orginal passage is found in Catherine's letter to Brother William of England (Scudder's "Letters of St. Catherine of Siena, p. 63):
"Such a man as this rejoices in everything; he does not make himself a judge of the servants of God, nor of any rational creature; nay, he rejoices in every condition and every type that he sees, saying, "Thanks be to Thee, eternal Father, that Thou hast many mansions in Thy House." And he rejoices more in the different kinds of men than he would do in seeing them all walk in the same way, for he sees the greatness of God's goodness more manifest. He joys in everything, and gets from it the fragrance of roses. As even as to a thing which he may expressly see to be sin, he does not pose as a judge, but rather regards it with true compassion, saying, "To-day it is thy turn, and to-morrow mine, unless it be for divine grace which preserves me."
This is not an isolated sentiment, but pervades her letters. In a "Letter to a Mantellata of St. Dominic" (p. 91), she writes:
"Beware lest thou do like mad and foolish people who want to sent themselves up to investigate and judge the deeds and habits of the servants of God. He who does this is entirely worthy of severe rebuke. Know that it would not be different from setting a law and rule to the Holy Spirit if we wished to make the servants of God all walk in our own way -- a thing which could never be done."
And from a letter to Sano Di Maco (p. 252):
"But if he will open his eyes, he will find the serpent of presumption under a false aspect, which plays the judge, judging in its own fashion, and not according to the holy and diverse ways in which God works with His creatures. Let human pride be ashamed and consent to see that in the House of the Eternal Father are many mansions. Let it not seek to impose a rule upon the Holy Spirit: for He is the Rule itself, Giver of the rule: nor let it measure Him who cannot be measured."
Truly a remarkable fourteenth century woman, our Catherine.